Filter cartridge, particularly for jug water purifiers

ABSTRACT

In a device for shutting off the flow of a fluid through a duct, preferably in a system for filtering drinking water, means for shutting off the duct comprise at least one obturator ( 14,22,35,43 ) disposed over a corresponding orifice ( 11 ) of the duct and means ( 15,23,36 ) for restraining the obturator ( 14,22,35,43 ) in a position such that the corresponding orifice ( 11 ) is not shut off, the restraining means being exposed to the flow of fluid through the duct and being able to undergo a change of state consequent upon the period of exposure to the flow in order to release the obturator ( 14,22,35 ) so that it shuts off the duct after a predetermined flow of fluid has taken place through the duct.

TECHNICAL FIELD

The present invention. relates to an improved filter cartridge,particularly for jug or carafe water purifiers, according to thepreamble to the main claim.

BACKGROUND ART

The use of filtering systems with replaceable cartridges for cleansingthe drinking water of organoleptically unpleasant odours and flavours iswidespread.

Typically, activated-carbon filters are used and these have to bereplaced after a predetermined number of filtering cycles. The cartridgecontains a bed of activated carbon and in turn separates twocompartments of a jug, for holding water to be filtered and filteredwater, respectively.

To prevent the user from being able to use the same cartridge for agreater number of cycles than is compatible with effective operation ofthe cartridge, these filtering systems generally have counters which canblock access to the jug to prevent new water from being admitted to thecompartment for water to be filtered once the count indicates that thefiltering capacity of the cartridge is probably exhausted.

The main disadvantage of these counter systems is that it is generallypossible to zero the countermand clear the access to the jug withoutreplacing the cartridge and thus to make further use of an exhaustedcartridge.

Although this does not lead to any particular problems beyond inadequatepurification of the water treated when the purpose of the system islimited to the cleansing of the water of unpleasant odours and flavours,clearly this system cannot be used with the necessary safety when thefiltering cartridge is required to cleanse the water being treated ofmicrobial and/or bacteriological loads, that is, when it is requiredactually to make the water drinkable.

In this case, it is essential for the flow of water through thefiltering system to be prevented once and for all as soon ascircumstances arise such that the filtering capacity of the cartridgeshould be considered to be exhausted, for example, after the treatmentof a predetermined number of litres of water to be made drinkable.Otherwise, the user would be drinking not only inadequately deodorizedwater, but water which is potentially polluted by bacteria and otherorganisms or substances hazardous to health.

Valves or similar mechanisms capable per se of shutting off a duct aftera predetermined flow has passed through it are known, for example, fromU.S. Pat. Nos. 4,681,677, 3,586,018, 3,503,507, 4,772,386 and 4,769,135.

The mechanisms described therein are used in various fields but none ofthem is suitable for direct application, as in the case of the presentinvention, to disposable filter cartridges such as those used in jugwater purifiers for domestic use.

DISCLOSURE OF THE INVENTION

The main aim of the present invention is to provide a filter cartridgewhich can be used quite safely for making water drinkable as well aspossibly cleansing it of undesired odours and flavours in jug or carafepurifiers for domestic use.

Within the scope of this aim, the object of the invention is to providea replaceable filter cartridge which can be produced easily andinexpensively so that the device for shutting off the flow of fluidbeing treated can be incorporated directly in the replaceable cartridgein order to block the cartridge once its filtering capacity isexhausted.

This and other objects are achieved by the invention by means of afilter cartridge formed in accordance with the following claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The characteristics and advantages of the invention will become clearer.from the following detailed description of some embodiments thereof,described by way of non-limiting example, with reference to the appendeddrawings, in which:

FIGS. 1 and 2 are schematic cross-sections of a first embodiment of areplaceable cartridge for filtering jugs or carafes according to theinvention, with a new cartridge and with an exhausted cartridge,respectively,

FIGS. 3 and 4 are schematic cross-sections of a second embodiment of thecartridge according to the invention in the same operative conditions asFIGS. 1 and 2, respectively,

FIGS. 5, 6 and 7, 8 are schematic cross-sections of a third and a fourthembodiment of the cartridge according to the invention, respectively, inthe same operative conditions as FIGS. 1 and 2, respectively.

BEST MODE OF CARRYING OUT THE INVENTION

In FIGS. 1 to 8, a filter cartridge, generally indicated 1, is of thetype normally used in jug-like containers in which the cartridge islocated removably in the duct between an upper compartment of the jug towhich the water to be filtered is admitted, and a lower compartment inwhich the filtered water is collected. An example of these jugs isdescribed in WO 96/13318.

In the cartridge 1, a lower beaker-like portion 2 and an upper portion 3which constitutes a frustoconical lid thereof, are shown. These portionsare joined together in the region of an intermediate flange 4.

The upper portion 3 has, in the upper region 6 of its frustoconicalshell 7, a plurality of slots 8 together constituting a first duct forthe admission of the water to be filtered to the cartridge 1.

The lower portion 2 contains a filtering means 9 of known composition,for example, a bed of activated carbon and, in its base 10, has aplurality of holes 11 together constituting a second duct through whichthe purified fluid can flow out of the cartridge towards the lowercompartment of the jug. A permeable membrane 13 is interposed betweenthe filtering means 9 and the base 10.

With specific reference now to a first embodiment of the invention shownin FIGS. 1 and 2, an obturator is provided for blocking the second ductconstituted by the holes 11 upon the exhaustion of the filteringcapacity of the filtering means 9, which is determined in dependence onthe number of litres of water treated, the obturator being constitutedby an impermeable disc 14 which is fixed to the face of the permeablemembrane 13 on the side facing the base 10 and which can be disposedover the holes 11 so as to shut off their through-orifices when it bearson the base 10. The membrane 13 is kept away from the base 10 so thatthe orifices of the holes 11 are normally open, by an annular spacer 15interposed between the base 10 and the membrane 13. The spacer 15constitutes means for restraining the obturator 14 in a position inwhich the corresponding orifices are not shut off and is made of a knownsynthetic material (which is used for making the capsules of somemedicinal preparations or for so-called slow-release drugs) which isinert for drinking purposes and is not dangerous to man and which candissolve slowly in contact with the flow of fluid (water) to befiltered. The means for restraining the obturator can thus undergo achange of state consequent upon the period of exposure to the flow ofwater in order to release the obturator so that it shuts off the secondduct, as shown in FIG. 2, after a predetermined flow of, fluid has takenplace through the filtering means 9 and the spacer 15 has consequentlybeen partially dissolved.

FIGS. 3 and 4 show a second embodiment of the invention in which theduct 20 to be shut off has a conical seat 21 for a spherical obturator22 which is kept in a position in which it does not shut off the duct bya spacer 23 interposed between the obturator and the base 10. The spacer23 in this case is constituted by a small cylinder of the same materialof which the spacer 15 is made.

In the embodiment of FIGS. 5 and 6, the duct 30 to be shut off is formedin a flange 31 located between a first membrane 32 which is disposedabove the filtering means and a second membrane 33 located in the upperportion 3 of the cartridge and serving as an abutment for a spring 34.This spring 34 is compressed between the second membrane 33 and aplate-like obturator 35 which, when disposed on the flange 31, can closethe duct 30. The duct is normally kept open by a spacer 36 interposedbetween the obturator 35 and the first membrane 32; this spacer is madeof a material similar to that of the preceding embodiments. As a resultof the dissolving of the spacer 36, the obturator is urged into closureover the duct 30 by the spring 34 (FIG. 6).

In a fourth embodiment of the invention, the duct to be shut off isconstituted by a chamber 40 defined between the base 10 and a permeablemembrane 41 fixed to the inside of the lower portion 2 of the cartridge.

The obturator for this duct is made of a material which expands greatlywhen put in contact with the fluid to be filtered, for example, apolymeric resin to which starch molecules cling. This material iscompressed to form the centre 42 of a capsule 43, the outer shell 44 ofwhich is constituted by an impermeable coating made of the samematerial, which is slowly soluble in water, as the spacers of theprevious embodiments.

As shown in FIG. 8, once the capsule 43 has been exposed to the flow offiltered water for sufficient time to dissolve the shell 44 at leastpartially, the centre 42 expands greatly thus shutting off therespective duct.

What is claimed is:
 1. If A water filter cartridge comprising acontainer having a first chamber having an inlet end and an outlet end,a supply of filtering material disposed in said first chamber, a secondchamber defined between two permeable walls one of which is adjacent theoutlet end of said first chamber and a shut-off means for controllingthe flow of water through the second chamber, said shut-off meanscomprising at least one capsule disposed in the second chamber andcomprised of a center portion of a material expandable upon contact withwater and an outer shell surrounding the center portion wherein theouter shell is comprised of a water soluble material which dissolvesupon contact with water whereby the center portion will expand when theouter shell dissolves to substantially fill said second chamber to blockthe flow of water therethrough.